On Thu, Aug 25, 2016 at 3:39 PM, Marek Polacek <pola...@redhat.com> wrote: > On Thu, Aug 25, 2016 at 11:17:37AM +0200, Richard Biener wrote: >> On Wed, Aug 24, 2016 at 7:43 PM, Marek Polacek <pola...@redhat.com> wrote: >> > The -Wlogical-not-parentheses deliberately doesn't warn when the RHS has >> > boolean type. But since in C the type of a comparison is int, we need >> > to check for tcc_comparison, too. >> > >> > Bootstrapped/regtested on x86_64-linux and ppc64le-redhat-linux, ok for >> > trunk? >> >> What about using truth_value_p ()? That also includes && and || (just >> in case those >> do not have boolean type). > > You're right that I should also handle || and && (done in this patch). But I > can't use truth_value_p because we want to warn for e.g. "!a == (a & b)".
But a & b isn't truth_value_p. a && b is. Do we want to warn about !a == (a && b)? Richard. > Bootstrapped/regtested on x86_64-linux, ok for trunk? > > 2016-08-25 Marek Polacek <pola...@redhat.com> > > PR c/77292 > * c-common.c (warn_logical_not_parentheses): Don't warn for > a comparison or a logical operator. > > * c-c++-common/Wlogical-not-parentheses-1.c: New test. > > diff --git gcc/c-family/c-common.c gcc/c-family/c-common.c > index 3feb910..3656c57 100644 > --- gcc/c-family/c-common.c > +++ gcc/c-family/c-common.c > @@ -1481,7 +1481,8 @@ warn_tautological_cmp (location_t loc, enum tree_code > code, tree lhs, tree rhs) > > /* Warn about logical not used on the left hand side operand of a comparison. > This function assumes that the LHS is inside of TRUTH_NOT_EXPR. > - Do not warn if RHS is of a boolean type. */ > + Do not warn if RHS is of a boolean type, a logical operator, or > + a comparison. */ > > void > warn_logical_not_parentheses (location_t location, enum tree_code code, > @@ -1489,7 +1490,10 @@ warn_logical_not_parentheses (location_t location, > enum tree_code code, > { > if (TREE_CODE_CLASS (code) != tcc_comparison > || TREE_TYPE (rhs) == NULL_TREE > - || TREE_CODE (TREE_TYPE (rhs)) == BOOLEAN_TYPE) > + || TREE_CODE (TREE_TYPE (rhs)) == BOOLEAN_TYPE > + || COMPARISON_CLASS_P (rhs) > + || TREE_CODE (rhs) == TRUTH_ANDIF_EXPR > + || TREE_CODE (rhs) == TRUTH_ORIF_EXPR) > return; > > /* Don't warn for !x == 0 or !y != 0, those are equivalent to > diff --git gcc/testsuite/c-c++-common/Wlogical-not-parentheses-1.c > gcc/testsuite/c-c++-common/Wlogical-not-parentheses-1.c > index e69de29..ba57437 100644 > --- gcc/testsuite/c-c++-common/Wlogical-not-parentheses-1.c > +++ gcc/testsuite/c-c++-common/Wlogical-not-parentheses-1.c > @@ -0,0 +1,25 @@ > +/* PR c/77292 */ > +/* { dg-do compile } */ > +/* { dg-options "-Wlogical-not-parentheses" } */ > + > + /* Test that we don't warn if rhs is a comparison or a logical op. */ > + > +int > +foo (int a, int b) > +{ > + int r = 0; > + r += !a == (a < b); > + r += !a == (a > b); > + r += !a == (a >= b); > + r += !a == (a <= b); > + r += !a == (a != b); > + r += !a == (a == b); > + r += !a == (a || b); > + r += !a == (a && b); > + r += !a == (!b); > + > + r += !a == (a ^ b); /* { dg-warning "logical not is only applied to the > left hand side of comparison" } */ > + r += !a == (a | b); /* { dg-warning "logical not is only applied to the > left hand side of comparison" } */ > + r += !a == (a & b); /* { dg-warning "logical not is only applied to the > left hand side of comparison" } */ > + return r; > +} > > Marek